Tokkai Hei 8-270772 published by the Japanese Patent Office in 1996 discloses a speed ratio control device of a toroidal continuously variable transmission which transmits an output torque of an engine to drive wheels of a vehicle at an arbitrary speed ratio. This prior art specifically discloses feedback correction of the speed ratio of the transmission as well as a torque shift error correction. The torque shift error is a speed ratio error due to a deformation of trunnions supporting power rollers of the transmission when the output torque of the engine, or in other words, the input torque of the transmission varies.